Given the amount of sheer unadulterated BASS that you can get out of a modular without even trying hard, I would suggest that you go with monitors that have at the very least 8" drivers for the low end. I use a pair of SF-era KRKs, myself...9000Bs...as "critical nearfields" with a Crest FA601 amp. However, be careful that what you get is actually rather flat; one monitor that I've learned to DREAD are the horrid Yamaha NS10Ms and the various descendants of those...they make everything sound like refried ass when you check your mix on more typical monitors. Some people swear by them; much of my time with them over the years found me swearing AT them. Just. Say. No.
Try and find something that's more "point source-ish", actually. Uli's reissued some of the Tannoy single-point ones for decent prices, but my money would be on the more-spendy powered Presonus Scepter 8s. But get the best thing you can afford...monitoring is 100% NOT the part you skimp on, as that subsystem of your studio is how you know what you're doing!